Recently, more and more products such as mobile information terminals and the like use an organic EL display device for a display screen. An organic EL display device is a display device of a self-light emission type that controls a plurality of pixels, each including a light emitting element, to form an image, and has an advantage of being low in the viewing angle dependence. Each of the pixels of the organic EL display device includes a switching transistor usable to write a video signal and a driving transistor usable to control an electric current flowing to the light emitting element.
A gate terminal of the driving transistor is connected with an output terminal (source or drain) of the switching transistor. With such a structure, a video signal that is input to the gate terminal of the driving transistor is controlled by an on/off operation of the switching transistor. In general, a pixel capacitor acting as a passive element that accumulates charges is connected between the gate terminal of the driving transistor and the output terminal of the switching transistor. The voltage of the pixel capacitor is applied to the gate terminal of the driving transistor, and an electric current in accordance with the voltage flows to the light emitting element (see, for example, Japanese Laid-Open Patent Publication No. 2008-51990).